Navigating the Hilbert space of elastic bell states in driven coupled waveguides

Externally driven arrays of coupled elastic waveguides have been shown to support nonseparable elastic superpositions of states that are analogous to entangled Bell states in a multipartite quantum system. Here, the “subsystems” correspond to spatial eigen modes characterized by the amplitude and phase difference between the waveguides. We show experimentally that the driving frequency, the relative amplitudes, and phases of the drivers applied to the waveguides, are critical parameters for exploring the elastic Bell states’ Hilbert space. We also demonstrate experimentally the capability of tuning the degree of nonseparability of the superpositions of elastic states. The degree of nonseparability is quantified by calculating the entropy of entanglement. Finally, in support of the experimental observations, we show theoretically that nonlinearity in the elastic behavior of the coupling medium (epoxy) and heterogeneities in the coupling along the waveguides can serve as design parameters in extending the range of the elastic Bell states’ Hilbert space that can be explored.